Originally Posted by ILLusion
Any gun that's not a v2 gearbox.
NiCad batteries will kick NiMH batteries around.
Keep your battery warm to improve performance.
+1 to all these points. I've seen many V2's break below about -5 C. On the other hand, both my ICS M4's have functioned very well in plenty of winter games. The mechbox shells are a bit thicker, and I am sure I'll break one some day but I haven't so far.
NiCads are much more forgiving in the cold than NiMh. Lithium are even better. The age and condition of your battery will play a bigger role in colder weather. Keeping your battery warm will make it perform better, as cooling them will reduce the reactivity inside them. A lot of our army equipment that runs on batteries either uses lithium rechargeables or will have a built in heater of some sort.
In the winter I find putting your GBB in a shoulder holster improves it's efficiency in the cold. Same with the mags. Those nylon secret service type rigs works very well.